A vehicle lighting device using a light emitting element as a light source is employed in front combination lamps and rear combination lamps. When the light emitting element is used in a lighting device, thermal management for the light emitting element is one important item. This is because the light emitting element has characteristics that light emitting efficiency is decreased due to a temperature rise of the element itself. In particular, in order to be mounted on a vehicle, the vehicle lighting device needs to maintain a function under an operating environment from a low temperature environment of −40° C. to a high temperature environment of 85° C. In this regard, the thermal management under the high temperature environment is important. In addition, the vehicle lighting device needs to be miniaturized, thereby precluding a heat radiating area from being sufficiently secured. Accordingly, the thermal management becomes more important. If a plurality of LED units previously unitized to be mountable on a board is simply mounted on a printed circuit board, the printed circuit board is increased in size, thereby resulting in an inevitably increased size of the vehicle lighting device. Incidentally, the lighting device includes those which have a light guide for guiding light emitted from the light emitting element.
If the thermal management or the fact that the printed circuit board is internally accommodated is considered, miniaturization of the vehicle lighting device cannot be achieved. As a result, an outer diameter of the vehicle lighting device is increased. An attachment unit in which the vehicle lighting device is attached to a lamp, for example, which emits the light from the vehicle lighting device, is disposed on an outer peripheral surface of the vehicle lighting device. In this case, the attachment unit is caused to have the larger outer diameter according to the diameter of the vehicle lighting device. In this regard, when the vehicle lighting device is generally attached to the lamp, a portion of the vehicle lighting device is protruded into the lamp. For this reason, an insertion port for inserting the vehicle lighting device is formed in the lamp. Since the attachment unit is attached to the lamp in the vicinity of the insertion port, the insertion port is increased in size so as to match the outer diameter of the vehicle lighting device. Therefore, if the diameter of the vehicle lighting device is increased, when a front surface of the vehicle lighting device is viewed from outside of the lamp, there is a problem in that a proportion occupied by a light non-emitting region which does not emit the light is relatively increased as compared to a light emitting region which emits the light such as the light emitting element.
The exemplary embodiments described herein aim to provide a vehicle lighting device which can decrease the proportion occupied by the light non-emitting region with respect to the light emitting region when viewed from the front.